Adding unit tests for PreviewsOptOutStoreSQL

components/previews/core/previews_black_list_item.cc

Index: components/previews/core/previews_black_list_item.cc
diff --git a/components/previews/core/previews_black_list_item.cc b/components/previews/core/previews_black_list_item.cc
index 9fd3286772ca7497406a48351b8cb89bc7fae591..59ba6cfe606c1f6265a255b8092d0272f9dccc72 100644
--- a/components/previews/core/previews_black_list_item.cc
+++ b/components/previews/core/previews_black_list_item.cc
@@ -50,11 +50,15 @@ void PreviewsBlackListItem::AddPreviewNavigation(bool opt_out,
   DCHECK_LE(opt_out_records_.size(), max_stored_history_length_);
 }
 
 bool PreviewsBlackListItem::IsBlackListed(base::Time now) const {
   DCHECK_LE(opt_out_records_.size(), max_stored_history_length_);
   return most_recent_opt_out_time_ &&
          now - most_recent_opt_out_time_.value() < max_black_list_duration_ &&
          total_opt_out_ >= opt_out_black_list_threshold_;
 }
 
+size_t PreviewsBlackListItem::OptOutRecordsSizeForTesting() const {
+  return opt_out_records_.size();
+}
+
 }  // namespace previews